The Southern Highlands receives generous rainfall, Robertson tops 1,100mm per year, Bowral around 800-900mm. For properties with large gardens, orchards or productive plantings, rainwater capture and storage is genuinely valuable: it’s free water, it’s soft (low mineral content from basalt and granite catchments), and it reduces reliance on mains supply for irrigation.
When a pool is removed, an interesting question sometimes arises: could the resources and space freed up by pool removal be redirected toward better water collection? This guide explores the relationship between pool removal and rainwater harvesting in the Highlands context, including the option of converting a pool to a tank, and the more common path of installing separate rainwater storage after removal.
Quick Answer (BLUF)
Removing a pool and replacing it with a purpose-designed rainwater tank or underground cistern can be a genuinely sensible water management upgrade for Southern Highlands properties, particularly rural-residential blocks with large gardens or orchards. A 20,000-50,000 litre rainwater tank costs $3,000-$10,000 and can supply significant irrigation and non-potable use. The key questions are site suitability, connection to the roof catchment, and whether storage above ground or below ground is preferred. Converting the pool shell directly to a water tank is possible in some cases but is complex, purpose-built tanks are usually better.
The Southern Highlands Rainfall Advantage
Unlike coastal Sydney or the Hunter, the Southern Highlands benefits from:
- High and reliable annual rainfall (distributed through the year, not strongly seasonal)
- Low summer temperatures reducing evaporation losses from open tanks
- Large property sizes in rural-residential areas, meaning large roof catchment areas and space for significant tank installations
- Productive gardens and orchards that benefit substantially from reliable irrigation water
The combination of abundant rainfall and productive garden uses makes rainwater harvesting more valuable per dollar invested here than in many other parts of NSW.
Converting a Pool to a Rainwater Tank: Is It Worth It?
Our dedicated guide on converting a pool to a water tank or dam covers this in detail. The brief summary:
Advantages:
- Avoids excavation and backfill costs, the existing excavation and shell become the vessel
- Creates a very large storage volume (most residential pools are 30,000-100,000 litres)
- Low carbon footprint compared to manufacturing a new tank
Significant challenges:
- Pool shells are not designed or watertight-tested for potable or even general irrigation water storage
- Existing cracks, osmotic blistering (fibreglass) or render delamination (concrete) create ongoing leak and water quality issues
- The pool’s plumbing is not configured for tank use, significant replumbing required
- Chemical residues from pool use may be difficult to fully flush
- Council approval for the change of use is required
- Covering the pool (to reduce evaporation and prevent debris and vector entry) adds significant cost
The realistic conclusion: Converting a pool to a water tank works best on properties with a large, structurally sound pool where the owners are willing to invest in proper conversion (professional sealing, replumbing, cover installation). For most properties, the challenges outweigh the savings compared to a purpose-built tank.
Purpose-Built Rainwater Tanks After Pool Removal
After removing the pool, the cleared space can accommodate purpose-built rainwater tanks. Options range from:
Above-ground polyethylene tanks: 10,000-25,000 litre slimline or round tanks. Low cost ($800-$3,000), readily available, easy to install. Most suitable when the tank area won’t be in a primary visual location. In the Southern Highlands’ cold winters, above-ground poly tanks may experience slight ice expansion in extreme frosts, this is generally tolerated by modern poly tank designs.
Above-ground corrugated steel tanks (Colorbond): Larger volumes, more aesthetically pleasing than poly tanks. Round tanks up to 75,000 litres. Cost $2,000-$8,000 for the tank plus installation. Common on rural-residential Highlands properties where a substantial water storage is part of the property’s character.
Underground concrete or polyethylene cisterns: Installed below ground, invisible from the surface, suitable for use directly above or near the old pool area (after sufficient settlement, six to twelve months minimum). Underground storage is space-efficient in more constrained backyards. Cost $5,000-$15,000 including excavation and installation.
Repurposing the existing excavation: If the pool removal is being planned with rainwater storage in mind, the contractor can modify the excavation methodology, instead of fully backfilling, the excavation volume can be reduced to accommodate an underground cistern placed in the base of the pit. This is a more complex project but eliminates the need for a separate cistern excavation.
Catchment Sizing: How Much Water Can You Collect?
A rough calculation for a typical Southern Highlands property:
- Bowral/Mittagong (800mm annual rainfall)
- 100m² of roof catchment area (a modest house)
- Collection efficiency of 80% (accounting for losses)
- Annual yield: 64,000 litres = 64,000L per year
This is a substantial volume, enough to supply a large vegetable garden and fruit trees throughout the year with storage to bridge dry periods.
For Robertson properties (1,100mm+ rainfall) with larger roof areas, the potential yield is even greater.
Planning the Connection
For rainwater harvesting to work, the tank must be connected to a significant roof catchment via gutters and downpipes. Key considerations:
- Downpipe location: The tank should be positioned close to a major downpipe to minimise the pipework required
- First-flush diverters: These bypass the first few litres of rain (which carry dust and bird droppings) before directing water to the tank, important for water quality
- Overflow: The tank overflow must be directed safely, typically to a dispersal area or stormwater connection
- Pump: Below-ground cisterns and tanks where the outlet is below the desired use point need a pump. Above-ground tanks can gravity-feed to lower areas
Wingecarribee Shire Council Requirements
Rainwater tanks in Wingecarribee Shire are generally complying development or exempt development for standard sizes and locations. The relevant policies are in the Wingecarribee DCP. Tanks over certain sizes, or underground cisterns, may require a CDC. Your supplier or a certifier can advise whether your specific proposal requires approval.
FAQs
Can I install a rainwater tank as part of the pool removal project?
Yes, coordinating tank installation with the pool removal is efficient. The contractor can prepare the base or excavation for the tank at the same time as managing the pool removal, reducing the total site disruption. Discuss this with your pool removal contractor at the quote stage.
Will a rainwater tank qualify for any rebate in NSW?
NSW Government rainwater tank rebates have varied over the years. Some water utilities offer rebates for tank installation. Check the current status with your water utility provider (Essential Water in some areas, private providers in others) and the NSW Government’s sustainability programs. Rebate programs can change year to year.
Is rainwater from the Southern Highlands safe to use for irrigation?
Yes, rainwater collected from a clean roof catchment with a first-flush diverter is safe for garden irrigation. It is soft (low mineral content), naturally close to neutral pH, and free of the chlorine and fluoride in mains water. For potable use (drinking), standard practice is to add a UV treatment or fine filtration stage.
How much water does a vegetable garden use in the Highlands?
A productive vegetable garden (say, 4 x 1.5m raised beds) in the Southern Highlands uses approximately 2,000-4,000 litres per week during the growing season. With reliable Highlands rainfall, supplementary irrigation is mainly needed December through March (the drier summer months). A 20,000-litre tank would cover approximately five to ten weeks of peak irrigation demand without any rainfall input.